"If only 2.1% of the population speaks English and it is used as a business language then it is most likely taught formally in schools. It is also likely this is the first time most people from Botswana learn it as a spoken language."

You are most likely mis-interpreting that statistic to conclude that only 2.1% of the population speaks English and that they learned the language in school.

Much more likely (the world over) is that there's a wide familiarity with a local pidgeon version of english containing heavy influences from the native language, local meter and speech patterns, and of course input from popular media - and that this is far more dominant than the official "learned in school" version of the language in everyday communication between ordinary people.

And it's that local english which the message appears to be written in.

If you are familiar with the "Pata Pata is the name of a dance we do down Johannesburg way" Cha cha track, the local english interludes may give some idea of the effect (although while Tswana is also spoken in South Africa, it's not the language in that song)